This Is Your Brain on Sugar (Trust Us, It’s Not Pretty)

Sugar acts like an addictive substance, lighting up the same areas of your brain as drugs like cocaine

Sugar can directly contribute to depression and increase anxiety

Too much sugar can create insulin resistance

Sugar — in all its different forms, from the naturally occurring sugars in fruit to high fructose corn syrup — can wreak all sorts of havoc on your brain. And that havoc runs the gamut from relatively minor (like causing your energy crash) to the seriously major (like contributing to dementia).

But why, exactly, is sugar so dangerous? What does it do the brain? And is there a better way to get the energy you need — without all the negative side effects to the brain?

This is your brain on sugar

All the cells in your body use glucose for energy. And because your brain is home to so many nerve cells, it ends up using the majority of glucose in your body for fuel — studies show the brain accounts for 60% of the body’s glucose utilization.

Your brain needs some glucose to function (Even those on the strictest keto diet get some glucose, or carbs, in their diet) — but on the typical American diet, it gets way more than it needs. The average American consumes 82 grams of added sugar per day — more than triple the World Health Organization’s recommendation of 25 grams per day.[1] And when it comes to sugar and the brain, more isn’t better.

Your brain is the control center for your body — and when there’s too much sugar in your system, it throws the control center out of whack. Too much sugar causes a cascade of negative side effects in your brain — and those negative side effects can affect everything from your mood to your diet to your energy levels.

Let’s take a look at some of the negative ways sugar impacts the brain:

Sugar can cause addiction…

Everyone knows you can easily get addicted to substances like heroin or cocaine — but turns out, sugar is just as addictive.

“The short-term reward circuitry in the brain that enhances dopamine production is directly enhanced by sugar consumption,” says neurologist David Perlmutter, MD, author of “Grain Brain.” “Consumption of sugar…stimulates specific areas of the brain that are linked to addiction. These areas are the same ones that light up on brain imaging studies when subjects are given cocaine.”

In a recent study, researchers used functional magnetic resonance imaging (fMRI) to study the changes in participants’ brains after consuming a meal of high-glycemic-index foods versus a meal with low-glycemic-index foods. Researchers found a significantly higher levels of activity in the areas of the brain responsible for reward and craving after the high-GI meal. They also found that participants who consumed a high-GI meal reported increased feelings of hunger.[2]

So in a nutshell: You eat sugar, you activate your brain’s reward center, and, as a result, you start craving more sugar. You’re hungry, so you go straight for more high-glycemic foods — and then you start the whole cycle over again. In other words, it’s a recipe for addiction.

…and symptoms of withdrawal

Just like any addiction, you’ll also go through withdrawal when you stop.

A 2002 study found that rats who were fed excessive amounts of sugar and then forced into “withdrawal” (either by withholding food or by treatment with naloxene, a drug that binds to the receptors in the brain’s reward system) experienced physical symptoms like teeth chattering, head shakes, and tremors.[3]

In addition to physical withdrawal symptoms, sugar withdrawal can also have side effects. Another study found that when put through a forced swim test, rats in sugar withdrawal were more likely to passively float than actively swim to escape, which indicated feelings of helplessness and depression.[4]

Sugar contributes to depression

Sugar can also have a negative impact on your mental health — particularly when it comes to depression and anxiety.

One of the primary causes of depression is the hormone serotonin (or, more specifically, the lack thereof) — and sugar messes with the body’s ability produce serotonin, which can lead to depression.

The first way sugar impacts serotonin production? In the gut. “Most serotonin [about 90%][5] is produced in the gut. If the function of your gut is compromised from overloading it with too much sugar, you’ll have trouble with important gut functions like digestion, immune cell formation, and serotonin production,” says nutrition expert Dan DeFigio, founder of BeatingSugarAddiction.com.

Too much sugar also impacts your brain’s ability to produce and utilize serotonin. “B vitamins — especially folic acid — are essential for the production of serotonin. A high-sugar diet forces your body to use up its B vitamins to metabolize the sugar, leaving none for the production of serotonin or other important uses,” says DeFigio.

Sugar can lead to anxiety

Not only can sugar contribute to depression, it also causes anxiety.

“Sugar abuse initiates a blood sugar roller coaster that can trigger anxiety attacks. When blood sugar levels crash, your brain becomes desperate for food, and your body can become shaky, weak, confused, and anxious in your hypoglycemic state. As blood sugar levels plummet, the brain reacts by sending out a panicked adrenaline alarm, leading to anxiety,” says DeFigio. “[In addition,] when you eat too much sugar, the amount of a protein called brain-derived neurotropic factor (BDNF) decreases. BDNF plays an important role in reducing anxiety, panic, and stress reactions, so a deficiency can exacerbate these conditions.”

Sugar causes insulin resistance — which impacts brain function

When we think of the hormone insulin, we think of regulating blood sugar — but it’s also an important part of brain function.

“As more dietary sugar is consumed, the hormone insulin becomes less effective. Insulin helps maintain the health and growth of brain cells,” says Perlmutter. “As things progress and blood sugar becomes more and more elevated, the brain becomes even more resistant to the important actions of insulin.” And as that happens, cognitive function declines.

A recent study, which followed over 5,000 participants over the course of a decade, found that people with high blood sugar had significantly faster rates of cognitive decline — and the higher the sugar, the swifter the decline.[6] In fact, people with type 2 diabetes are twice as likely to develop dementia — which is why Alzheimer’s disease is now referred to as type 3 diabetes.[7]

Why ketones are the way to go when it comes to energy

Clearly, sugar is a nightmare when it comes to brain function. But luckily, there’s an alternative that will get your brain the energy it needs without all the negative side effects — and that’s ketones.

A ketogenic diet — like the Bulletproof diet — gives the brain more efficient fuel than a diet heavy in carbohydrates (which creates excess glucose). When your brain relies on ketones for energy, it performs at a higher level, increasing cognitive function and protecting the brain from a variety of degenerative diseases (for example, a recent study found that a ketogenic diet produced enhanced mitochondrial gene expression in the hippocampus, the area of the brain responsible for learning and memory).[8]

“By and large, a diet that favors sugar and carbs is a diet that steers a person away from burning fat. And that’s really threatening for brain function. Burning fat, and not sugar, is the ideal scenario for brain functionality,” says Perlmutter. “Ketones set the stage for brain health and function both directly by serving as super fuels for brain cells, as well as by triggering expression of our DNA that allows us to create chemicals that actually enhance the growth of new brain cells as well as their connection to each other.”

Deanna deBara is a freelance writer and journalist based in Portland, OR. Deanna covers mostly health and wellness topics, and you can find her work in Greatist, Playboy, Men's Health, and other health-conscious corners of the internet.